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Full text of "The manufacture and properties of iron and steel"

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BLAST PURNA.OE.                                           71
stance, all those depending on the limestone, this being determined by the impurities to be fluxed. In the American furnace the factors beyond the control of the smelter required only 206 pounds of coke, while in the English furnaces 382 pounds were needed, a difference of 176 pounds. Inasmuch as fifty per cent, of all the energy is lost in the escaping gases, these factors alone account for an extra 352 pounds of fuel in the English furnace.
(13)   The factors which are more or less under control are practically the same in both cases, giving a total of 7.5 per cent, in Pittsburg and 8.6 per cent, in Cleveland.
(14)   The loss in the tunnel head gases is the only great item presenting any hope for future economies.   In the Cleveland'practice the ratio1 of CO to C02 was 2.11.    In Pittsburg it was 2.35. It has been stated by Bell that a ratio better than 2 to 1 can hardly be hoped for, but this is a mistake, as -many furnaces can show better results. A ratio of 1.5 to 1 can be obtained, while the future may see even greater economy.
SEC. Urn.—Tunnel liead gases.—At every blast furnace .the tunnel head gases are sufficient to heat the stoves and raise steam for the blowing engine and the pumps, while at many plants there is a surplus above these needs which is used to generate steam power or electric energy. It is clear that any right system of bookkeeping will give credit to the furnace for this power at a fair price, which, in a plant equipped with proper boilers and engines, will amount to about 25 cents per ton of iron. Modern progress tends to reduce the amount of fuel per ton of iron, either by more skilful management or by hotter blast, or by concentration of the ore, or by the refrigeration of the. air, so the question arises whether a reduction in fuel may not seriously detract both from the volume and the heat value of the gas, with the result that a furnace might no longer be self-supporting and that in place of a credit for surplus power there would be a debit for extra coal.
The investigation of this question is simplified by taking as a basis a ton of coke and not a ton of iron, for the capacity of a furnace is limited not so much by the amount 6f ore and stone as by the amount of fuel. Given a furnace using 2500 pounds of coke per ton of iron, and let the working conditions be bettered so that only 2000 pounds are needed, and the product will be increased 25 per cent. The blowing engine is capable of delivering just so